OBJECTIVE: Identify mechanisms for CNS damage during SIV infection of macaques and assess extent of encephalitis. Provide matched samples of fixed and frozen brains for pathologic evaluation. RESULTS AIDS disease progression often results in clinical dementia and other neuropsychiatric illnesses. Pathologic examination of disease human brains revealed extensive encephalitis. We are studying the pathology of diseased rhesus brains and providing fresh-frozen samples from these same brains to elucidate morphologic markers of disease and underlying changes in neurotransmitted function and changes in other brain chemical distributions. In parallel, we are examining the changes in cerebral spinal fluid composition as a marker for CNS damage in the macaque. These studies have used residual materials from other infection experiments. FUTURE DIRECTIONS Continue to develop correlations between CSF markers and neurologic impairment. Assess effects of varying virus strain and route of inoculation on the probability of inducing CNS damage. KEY WORDS AIDS, dementia, CNS, pathology